Monday, February 26, 2007

Solid-State NMR Update - October 2006

Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 3-4, October, 2006
pp. 125-129

Title: 3-Methylglutaric acid as a 13C solid-state NMR standard
Authors: Barich, Dewey H.a; Gorman, Eric M.a; Zell, Mark T.b; Munson, Eric J.a
Affiliations: a. Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Ave., Lawrence, KS 66047, USA
b. Pfizer Global Research and Development, Analytical Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105, USA
Abstract (English):

The calibration of a solid-state NMR spectrometer requires setting the magic angle, setting the reference and decoupler frequencies, ensuring that the magnetic field is homogeneous across the sample volume, optimizing the signal-to-noise ratio, determining the p/2 pulse durations, and optimizing the Hartman–Hahn matching condition. Each task has one or more widely accepted standards, such as potassium bromide for setting the magic angle, adamantane for optimizing magnet homogeneity, and hexamethylbenzene or glycine for measuring the signal-to-noise ratio. We show that all of these tasks can be performed using 3-methylglutaric acid (MGA). In the case of high-powered decoupling, the CH2 and CH carbon peaks of MGA provide an opportunity to evaluate the decoupling in a manner that is superior to any of the commonly used standard compounds. Thus, MGA can be used as a single solid-state NMR standard compound to perform all calibration steps except for magnet shimming.

Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 3-4, October, 2006
pp. 130-134

Title: Decoupling residual dipolar coupling between 13C and14N spin pairs in CPMAS NMR
Authors: Orr, Robin M.a; Duer, Melinda J.a
Affiliations: a. University Chemical Laboratory, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
Abstract (English):

Decoupling of the residual dipolar coupling between 13C and14N nuclei is investigated experimentally in a triple resonance experiment. It is shown that pulsed decoupling can be used to give enhanced sensitivity and reduced line widths and the technique is illustrated using short peptides.

Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 3-4, October, 2006
pp. 162-170

Title: Solid-state 17O NMR study of the electric-field-gradient and chemical shielding tensors in polycrystalline g-glycine
Authors: Yamada, Kazuhikoa; Honda, Hisashib; Yamazaki, Toshioa; Yoshida, Mitsuruc
Affiliations: a. NMR Spectroscopy Team, RIKEN Genomic Sciences Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama-shi, Kanagawa-ken 230-0045, Japan
b. International Graduate School of Arts and Sciences, Yokohama City University, 22-2 Seto, Kanawaza, Yokohama 236-0027, Japan
c. Analytical Science Division, National Food Research Institute, 2-1-12 Kannondai, Tsukuba 305-8642, Japan
Keywords: Solid-state 17O NMR; Chemical shielding tensor; Electric-field-gradient tensor; g-glycine
Abstract (English):

We report the first experimental determination of the carboxylate oxygen electric-field-gradient (EFG) and chemical shielding (CS) tensors in polycrystalline g-glycine. Analysis of magic-angle spinning (MAS) and stationary 17O NMR spectra of [17O]-g-glycine obtained at 9.4, 14.1, 16.4, and 18.8T yields the magnitudes of the 17O EFG and CS tensors and the relative orientations between the two tensors. Extensive quantum chemical calculations at both the restricted Hartree–Fock and density functional levels have been performed to present the absolute tensor orientations in term of the molecular frame. We have demonstrated that 17O NMR tensor information could be unambiguously derived by the multiple field analyses of stationary 17O NMR spectra.

Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 3-4, October, 2006
pp. 171-181

Title: Vanadium-51 solid-state NMR electric field gradient tensors: A DFT-embedded ion and isolated cluster study of crystalline vanadium oxides
Author: Gee, Becky A.a
Affiliations: a. Department of Chemistry and Biochemistry, 1 University Plaza, Long Island University, Brooklyn Campus, Brooklyn, NY 11201, USA
Keywords: Vanadium-51; Nuclear magnetic resonance (NMR); Density functional theory (DFT); Embedded ion; Embedded cluster; Electric field gradient (EFG); Quadrupole coupling; Orthovanadates; Vanadium oxides
Abstract (English):

Density functional theory (DFT) calculations (6–311+G(2d,p)/B3LYP level of theory) of 51V electric field gradient (EFG) tensor elements are performed for embedded and isolated cluster models of orthovanadates. The structural models used to calculate the EFGs of 51V are (I) an isolated H4VO4+ cluster, (II) an isolated HnVO4n-3 cluster (n=number of next-neighbor cations) (III) an isolated orthovanadate anion, VO4-x, and (IV) a VO4-x ion embedded in a finite point-charge array whose electrostatic potential, at the embedded ion, is equivalent to that of the infinite lattice. For models III and IV, a charge x is assigned estimating the covalence of the system. Models III and IV provide results in good agreement with the experiment. Calculations, employing the embedded and isolated VO4-x models, are used to discuss site assignments for AlVO4. Correlations between quadrupole coupling parameters and deviations of the orthovanadate structure from ideal tetrahedral symmetry are shown.

Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 3-4, October, 2006
pp. 198-202

Title: First evidence of multiple Ca sites in amorphous slag structure: Multiple-quantum MAS NMR spectroscopy on calcium-43 at high magnetic field
Authors: Shimoda, Keijia; Tobu, Yasuhiroa; Kanehashi, Kojia; Nemoto, Takahirob; Saito, Kojia
Affiliations: a. Advanced Technology Research Laboratories, Nippon Steel Corporation, 20-1 Shintomi, Futtsu 293-8511, Japan
b. JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan
Abstract: No Abstract

Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006
pp. 61-68

Title: 14N nuclear quadrupole resonance of some sulfa drugs
Authors: Blinc, Roberta, b; Seliger, Janeza, c; Zidansek, Aleksandera, b; Zagar, Veselkoa; Milia, Fanid; Robert, Hectore
Affiliations: a. J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
b. Jožef Stefan International Postgraduate School, Jamova 39, 1000 Ljubljana, Slovenia
c. Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
d. NCSR Demokritos, Aghia Paraskevi Attikis, Athens, Greece
e. GE Security, Quantum Magnetics, Inc, 15175 Innovation Dr, San Diego, CA 92128, USA
Keywords: Polymorphs; Sulfa drugs; 14N nuclear quadrupole resonance
Abstract (English):

The 14N nuclear quadrupole double resonance spectra of different polymorphs of sulfanilamide, sulfadiazine, sulfamerazine and sulfamethazine have been measured and the 14N quadrupole coupling tensors have been determined. The obtained 14N spectra are compared with those of other sulfa drugs like sulfathiazole. It is shown that different polymorphs can be easily discriminated. The application of this technique for non-destructive analysis, polymorph determination and quality control in the production of pharmaceuticals is stressed.

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